DESCRIPTION: In this project sterically stabilized liposomes will be used for photoinduced fusion. Liposomes will be characterized in which polymerization within the bilayer results in destabilization and release of trapped contents. The basic physical characterization studies will be applied to liposome-cell interaction studies, with the goal of efficient photoinduced delivery of liposomal contents to cells having endocytotic activity. Thus, these studies will have an impact on the use of photosensitized liposomes for the localized delivery of drugs to cells. In this application, experiments are proposed for use of visible light to induce release of trapped agents from sterically stabilized liposomes prepared with lipids containing polyethylene glycol at the surface and polymerizable groups near the end of the chain. In the revision, emphasis has been placed on the biophysical characterization of uncharged PEG-lipids that can be prepared in a short synthetic sequence. Dr. Deborah E. Leckband (Department of Chemical Engineering, University of Illinois) has been added as a collaborator to measure surface forces in monolayers of PEG-lipids.